title: [Mechanisms underlying the improvement of arterial oxygenation using positive end-expiratory pressure during surgery under sevoflurane anesthesia and propofol anesthesia: a retrospective clinical study].
abstract: BACKGROUND
  The use of positive end-expiratory pressure (PEEP) is a practical intervention to improve oxygenation during anesthetic management; however, the underlying mechanisms have not been elucidated.
  
  
  METHODS
  Parameters of ventilator settings and results of arterial blood gas analyses were collected from medical records of adult patients undergoing surgery under general anesthesia with pressure-controlled ventilation in our hospital from January 2009 to March 2010. We analyzed the changes in dynamic compliance (Cdyn) and alveolar-arterial oxygen difference (A-aDo2).
  
  
  RESULTS
  A total of 139 patients were enrolled; anesthesia was maintained with sevoflurane in 82 patients, and with propofol in 57 patients. After the application of PEEP, significant decreases in A-aDo2 were accompanied with significant increases in Cdyn under sevoflurane anesthesia. However, significant decreases in A-aDo2 were not always accompanied by significant increases in C(dyn) under propofol anesthesia.
  
  
  CONCLUSIONS
  These results suggest that the mechanisms for improved oxygenation by PEEP under sevoflurane anesthesia are different from those under propofol anesthesia. The improved oxygenation after the application of PEEP under sevoflurane anesthesia is mainly due to reduction of atelectasis, whereas reduction of atelectasis as well as reduction of intrapulmonary shunt is associated with the improved oxygenation after the application of PEEP under propofol anesthesia.
authors.affiliation: Department of Anesthesiology, Faculty of Medicine, The University of Tokyo, Tokyo 113-8655.
authors.forename: Gaku
authors.initials: G
authors.lastname: Kawamura
authors.forename: Takayuki
authors.initials: T
authors.lastname: Kitamura
authors.forename: Ikuo
authors.initials: I
authors.lastname: Homma
authors.forename: Yoshitsugu
authors.initials: Y
authors.lastname: Yamada
mesh_terms: D000368:Aged; D000768:Anesthesia, General; D001158:Arteries; D005260:Female; D006801:Humans; D007432:Intraoperative Period; D008170:Lung Compliance / Q000502:physiology; D008297:Male; D008738:Methyl Ethers; D010100:Oxygen / Q000097:blood*; D011175:Positive-Pressure Respiration; D015742:Propofol; D012189:Retrospective Studies; D000077149:Sevoflurane
chemical_list: D008738:Methyl Ethers; D000077149:Sevoflurane; D010100:Oxygen; D015742:Propofol